The present invention relates to a method for the production of hydrogen, and more particularly to the continuous production of hydrogen under anaerobic conditions using metal as an active catalyst.
The use of hydrogen as an alternative fuel or power source is receiving wide attention in both political and technical arenas. There is a need for the efficient production of hydrogen for use as a fuel in both vehicular and stationary engines and fuel cell systems. One reason for this attention lies in the ability of hydrogen to burn cleanly without producing any toxic by-products. While hydrogen is a clean and renewable energy resource, it is both expensive to produce in a pure form and unsafe to store in quantity due to its combustibility. Moreover, hydrogen is expensive and heavy when stored in containers of practical size.
It is known that electropositive elements with a greater negative standard electrode potential than hydrogen displace hydrogen from water or aqueous solutions of acid or alkali. This principle forms the basis of metal displacement reactions used in the preparation of hydrogen in the laboratory. However, because the metal is consumed during the reaction, this process is cost prohibitive. Also, the conversion rate of the reaction is extremely low unless the water or aqueous solution has been heated to very high temperatures which results in a low overall efficiency and thus it has no current practical commercial utility. Therefore, it is not a practical method of hydrogen production from an industrial point of view. If the metal could be regenerated easily, then such metal displacement reactions could have practical uses beyond preparation of hydrogen in the laboratory.
One example of generating hydrogen based upon the reaction is disclosed in U.S. Pat. No. 4,547,356 by Papineau. Papineau suggested that hydrogen may be generated by the catalytic decomposition of steam at temperatures of 1000xc2x0 to 2000xc2x0 F. (540xc2x0 to 1094xc2x0 C.) to form hydrogen and supposedly oxygen. Papineau contends temperatures, the steam will disassociate in the presence of xe2x80x9ca catalyst of a web-like cellular structure defined by interconnected metal filaments comprising iron, copper, silver, nickel, palladium, platinum, or iron-nickel and molybdenumxe2x80x9d and that the hydrogen can then be separated from the oxygen with a diffusion-based separation membrane, e.g. palladium. Water or steam is thermodynamically incapable of decomposing into hydrogen and oxygen within the stated temperatures. Papineau continues to assert that more hydrogen will be produced by the process than will be required for reactivating the catalyst when it has become deactivated because of use.
Another example of generating hydrogen based upon this same reaction is disclosed in U.S. Pat. No. 5,510,201 by Werth. Werth disclosed a system for generating hydrogen at a faster rate by reacting particles of an activated iron reactant with heated water (up to 450xc2x0 C.) in a fluidized bed-type reactor. The reaction results in an increased rate of hydrogen production along with spent metal oxide particles. Werth""s method and system utilizes the heated water to reduce the metal oxide back to metal to recharge the system.
Accordingly, it is an object of the present invention to provide a new and improved method for the continuous production of hydrogen at a low cost.
It is a further object of the present invention to provide a new and improved method for the continuous production of hydrogen which is easy and relatively inexpensive to regenerate.
It is still a further object of the present invention to provide a new and improved method for the continuous production of hydrogen to be used as a clean fuel source that continually feeds fuel to an energy-producing device such as a heat engine or a fuel cell.
Further and other objects of the present invention will become apparent from the description contained herein.
In accordance with one aspect of the present invention, the foregoing and other objects are achieved by a method for the continuous production of hydrogen comprising reacting a metal catalyst with a degassed aqueous solution of an organic acid within a reaction vessel under anaerobic conditions at a constant temperature of xe2x89xa680xc2x0 C. and at a pH ranging from about 4 to about 9. The reaction forms a metal oxide when the metal catalyst reacts with the water component of the organic acid solution while generating hydrogen, then the organic acid solution reduces the metal oxide thereby regenerating the metal catalyst and producing water, thus permitting the oxidation and reduction to reoccur in a continual reaction cycle.